Relevance of urinary bladder models to clinical problems and to antibiotic evaluation

Applications and shortcomings of models of the bladder which employ urine as a medium have been described. A 'continuous culture' model was no better than conventional susceptibility tests in predicting response of patients with acute uncomplicated urinary infections to amoxicillin, but gave a good correlation with a mouse infection protection test for synergy studies with mecillinam and ampicillin. Some Enterobacteriaceae destroyed high concentrations of amoxicillin in urine under conditions resembling the milieu of the infected human bladder. Destruction was enhanced at increased residual urinary volumes and did not occur in the presence of clavulanic acid. The beneficial effects of clavulanic acid at urinary, as opposed to tissue, concentrations may be due to its antibacterial, as well as its antienzymic, activity.